[ViewVC] Diff of: cvs/JSON-XS/XS.pm

Comparing JSON-XS/XS.pm (file contents):
Revision 1.10 by root, Fri Mar 23 17:40:29 2007 UTC vs.
Revision 1.23 by root, Sun Mar 25 21:19:13 2007 UTC

 JSON::XS - JSON serialising/deserialising, done correctly and fast
 =head1 SYNOPSIS
  use JSON::XS;
+ # exported functions, they croak on error
+ # and expect/generate UTF-8
+ $utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
+ $perl_hash_or_arrayref  = from_json $utf8_encoded_json_text;
+ # objToJson and jsonToObj aliases to to_json and from_json
+ # are exported for compatibility to the JSON module,
+ # but should not be used in new code.
+ # OO-interface
+ $coder = JSON::XS->new->ascii->pretty->allow_nonref;
+ $pretty_printed_unencoded = $coder->encode ($perl_scalar);
+ $perl_scalar = $coder->decode ($unicode_json_text);
 =head1 DESCRIPTION
 This module converts Perl data structures to JSON and vice versa. Its
 primary goal is to be I<correct> and its secondary goal is to be
 =head2 FEATURES
 =over 4
-=item * correct handling of unicode issues
+=item * correct unicode handling
 This module knows how to handle Unicode, and even documents how and when
 it does so.
 =item * round-trip integrity
 When you serialise a perl data structure using only datatypes supported
 by JSON, the deserialised data structure is identical on the Perl level.
-(e.g. the string "2.0" doesn't suddenly become "2").
+(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
+like a number).
 =item * strict checking of JSON correctness
-There is no guessing, no generating of illegal JSON strings by default,
+There is no guessing, no generating of illegal JSON texts by default,
 and only JSON is accepted as input by default (the latter is a security
 feature).
 =item * fast
 interface.
 =item * reasonably versatile output formats
 You can choose between the most compact guarenteed single-line format
-possible (nice for simple line-based protocols), a pure-ascii format (for
+possible (nice for simple line-based protocols), a pure-ascii format
-when your transport is not 8-bit clean), or a pretty-printed format (for
+(for when your transport is not 8-bit clean, still supports the whole
-when you want to read that stuff). Or you can combine those features in
+unicode range), or a pretty-printed format (for when you want to read that
-whatever way you like.
+stuff). Or you can combine those features in whatever way you like.
 =back
 =cut
 package JSON::XS;
+use strict;
 BEGIN {
-   $VERSION = '0.3';
+   our $VERSION = '0.8';
-   @ISA = qw(Exporter);
+   our @ISA = qw(Exporter);
-   @EXPORT = qw(to_json from_json);
+   our @EXPORT = qw(to_json from_json objToJson jsonToObj);
    require Exporter;
    require XSLoader;
    XSLoader::load JSON::XS::, $VERSION;
 }
 The following convinience methods are provided by this module. They are
 exported by default:
 =over 4
-=item $json_string = to_json $perl_scalar
+=item $json_text = to_json $perl_scalar
 Converts the given Perl data structure (a simple scalar or a reference to
 a hash or array) to a UTF-8 encoded, binary string (that is, the string contains
 octets only). Croaks on error.
-This function call is functionally identical to C<< JSON::XS->new->utf8->encode ($perl_scalar) >>.
+This function call is functionally identical to:
+   $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
+except being faster.
-=item $perl_scalar = from_json $json_string
+=item $perl_scalar = from_json $json_text
 The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to
-parse that as an UTF-8 encoded JSON string, returning the resulting simple
+parse that as an UTF-8 encoded JSON text, returning the resulting simple
 scalar or reference. Croaks on error.
-This function call is functionally identical to C<< JSON::XS->new->utf8->decode ($json_string) >>.
+This function call is functionally identical to:
+   $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
+except being faster.
 =back
 =head1 OBJECT-ORIENTED INTERFACE
 The object oriented interface lets you configure your own encoding or
 decoding style, within the limits of supported formats.
 strings. All boolean flags described below are by default I<disabled>.
 The mutators for flags all return the JSON object again and thus calls can
 be chained:
-   my $json = JSON::XS->new->utf8(1)->space_after(1)->encode ({a => [1,2]})
+   my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
    => {"a": [1, 2]}
 =item $json = $json->ascii ([$enable])
-If C<$enable> is true (or missing), then the C<encode> method will
+If C<$enable> is true (or missing), then the C<encode> method will not
-not generate characters outside the code range C<0..127>. Any unicode
+generate characters outside the code range C<0..127> (which is ASCII). Any
-characters outside that range will be escaped using either a single
+unicode characters outside that range will be escaped using either a
-\uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, as per
+single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
-RFC4627.
+as per RFC4627.
 If C<$enable> is false, then the C<encode> method will not escape Unicode
-characters unless necessary.
+characters unless required by the JSON syntax. This results in a faster
+and more compact format.
-  JSON::XS->new->ascii (1)->encode (chr 0x10401)
+  JSON::XS->new->ascii (1)->encode ([chr 0x10401])
-  => \ud801\udc01
+  => ["\ud801\udc01"]
 =item $json = $json->utf8 ([$enable])
 If C<$enable> is true (or missing), then the C<encode> method will encode
-the JSON string into UTF-8, as required by many protocols, while the
+the JSON result into UTF-8, as required by many protocols, while the
 C<decode> method expects to be handled an UTF-8-encoded string.  Please
 note that UTF-8-encoded strings do not contain any characters outside the
-range C<0..255>, they are thus useful for bytewise/binary I/O.
+range C<0..255>, they are thus useful for bytewise/binary I/O. In future
+versions, enabling this option might enable autodetection of the UTF-16
+and UTF-32 encoding families, as described in RFC4627.
 If C<$enable> is false, then the C<encode> method will return the JSON
 string as a (non-encoded) unicode string, while C<decode> expects thus a
 unicode string.  Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
 to be done yourself, e.g. using the Encode module.
+Example, output UTF-16BE-encoded JSON:
+  use Encode;
+  $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
+Example, decode UTF-32LE-encoded JSON:
+  use Encode;
+  $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
 =item $json = $json->pretty ([$enable])
 This enables (or disables) all of the C<indent>, C<space_before> and
 C<space_after> (and in the future possibly more) flags in one call to
 generate the most readable (or most compact) form possible.
+Example, pretty-print some simple structure:
    my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
    =>
    {
       "a" : [
 If C<$enable> is true (or missing), then the C<encode> method will use a multiline
 format as output, putting every array member or object/hash key-value pair
 into its own line, identing them properly.
 If C<$enable> is false, no newlines or indenting will be produced, and the
-resulting JSON strings is guarenteed not to contain any C<newlines>.
+resulting JSON text is guarenteed not to contain any C<newlines>.
-This setting has no effect when decoding JSON strings.
+This setting has no effect when decoding JSON texts.
 =item $json = $json->space_before ([$enable])
 If C<$enable> is true (or missing), then the C<encode> method will add an extra
 optional space before the C<:> separating keys from values in JSON objects.
 If C<$enable> is false, then the C<encode> method will not add any extra
 space at those places.
-This setting has no effect when decoding JSON strings. You will also most
+This setting has no effect when decoding JSON texts. You will also
-likely combine this setting with C<space_after>.
+most likely combine this setting with C<space_after>.
+Example, space_before enabled, space_after and indent disabled:
+   {"key" :"value"}
 =item $json = $json->space_after ([$enable])
 If C<$enable> is true (or missing), then the C<encode> method will add an extra
 optional space after the C<:> separating keys from values in JSON objects
 members.
 If C<$enable> is false, then the C<encode> method will not add any extra
 space at those places.
-This setting has no effect when decoding JSON strings.
+This setting has no effect when decoding JSON texts.
+Example, space_before and indent disabled, space_after enabled:
+   {"key": "value"}
 =item $json = $json->canonical ([$enable])
 If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
 by sorting their keys. This is adding a comparatively high overhead.
 If C<$enable> is false, then the C<encode> method will output key-value
 pairs in the order Perl stores them (which will likely change between runs
 of the same script).
 This option is useful if you want the same data structure to be encoded as
-the same JSON string (given the same overall settings). If it is disabled,
+the same JSON text (given the same overall settings). If it is disabled,
 the same hash migh be encoded differently even if contains the same data,
 as key-value pairs have no inherent ordering in Perl.
-This setting has no effect when decoding JSON strings.
+This setting has no effect when decoding JSON texts.
 =item $json = $json->allow_nonref ([$enable])
 If C<$enable> is true (or missing), then the C<encode> method can convert a
 non-reference into its corresponding string, number or null JSON value,
 which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
 values instead of croaking.
 If C<$enable> is false, then the C<encode> method will croak if it isn't
-passed an arrayref or hashref, as JSON strings must either be an object
+passed an arrayref or hashref, as JSON texts must either be an object
 or array. Likewise, C<decode> will croak if given something that is not a
 JSON object or array.
+Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
+resulting in an invalid JSON text:
+   JSON::XS->new->allow_nonref->encode ("Hello, World!")
+   => "Hello, World!"
 =item $json = $json->shrink ([$enable])
 Perl usually over-allocates memory a bit when allocating space for
 strings.  This flag optionally resizes strings generated by either
 C<encode> or C<decode> to their minimum size possible. This can save
-memory when your JSON strings are either very very long or you have many
+memory when your JSON texts are either very very long or you have many
 short strings. It will also try to downgrade any strings to octet-form
 if possible: perl stores strings internally either in an encoding called
 UTF-X or in octet-form. The latter cannot store everything but uses less
 space in general.
 In the future, this setting might control other things, such as converting
 strings that look like integers or floats into integers or floats
 internally (there is no difference on the Perl level), saving space.
+=item $json = $json->max_depth ([$maximum_nesting_depth])
+Sets the maximum nesting level (default C<8192>) accepted while encoding
+or decoding. If the JSON text or Perl data structure has an equal or
+higher nesting level then this limit, then the encoder and decoder will
+stop and croak at that point.
+Nesting level is defined by number of hash- or arrayrefs that the encoder
+needs to traverse to reach a given point or the number of C<{> or C<[>
+characters without their matching closing parenthesis crossed to reach a
+given character in a string.
+Setting the maximum depth to one disallows any nesting, so that ensures
+that the object is only a single hash/object or array.
+The argument to C<max_depth> will be rounded up to the next nearest power
+of two.
+See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
-=item $json_string = $json->encode ($perl_scalar)
+=item $json_text = $json->encode ($perl_scalar)
 Converts the given Perl data structure (a simple scalar or a reference
 to a hash or array) to its JSON representation. Simple scalars will be
 converted into JSON string or number sequences, while references to arrays
 become JSON arrays and references to hashes become JSON objects. Undefined
 Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
 nor C<false> values will be generated.
-=item $perl_scalar = $json->decode ($json_string)
+=item $perl_scalar = $json->decode ($json_text)
-The opposite of C<encode>: expects a JSON string and tries to parse it,
+The opposite of C<encode>: expects a JSON text and tries to parse it,
 returning the resulting simple scalar or reference. Croaks on error.
 JSON numbers and strings become simple Perl scalars. JSON arrays become
 Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
 C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
 =back
 =head1 MAPPING
 This section describes how JSON::XS maps Perl values to JSON values and
 vice versa. These mappings are designed to "do the right thing" in most
 =over 4
 =item object
 A JSON object becomes a reference to a hash in Perl. No ordering of object
-keys is preserved.
+keys is preserved (JSON does not preserver object key ordering itself).
 =item array
 A JSON array becomes a reference to an array in Perl.
 =item hash references
 Perl hash references become JSON objects. As there is no inherent ordering
 in hash keys, they will usually be encoded in a pseudo-random order that
 can change between runs of the same program but stays generally the same
-within the single run of a program. JSON::XS can optionally sort the hash
+within a single run of a program. JSON::XS can optionally sort the hash
 keys (determined by the I<canonical> flag), so the same datastructure
 will serialise to the same JSON text (given same settings and version of
 JSON::XS), but this incurs a runtime overhead.
 =item array references
    $x *= 1;     # same thing, the choise is yours.
 You can not currently output JSON booleans or force the type in other,
 less obscure, ways. Tell me if you need this capability.
+=item circular data structures
+Those will be encoded until memory or stackspace runs out.
 =back
 =head1 COMPARISON
 As already mentioned, this module was created because none of the existing
 JSON modules could be made to work correctly. First I will describe the
 Has problems handling many Perl values (e.g. regex results and other magic
 values will make it croak).
 Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
-which is not a valid JSON string.
+which is not a valid JSON text.
 Unmaintained (maintainer unresponsive for many months, bugs are not
 getting fixed).
 =item JSON::Syck 0.21
 Very buggy (often crashes).
 Very inflexible (no human-readable format supported, format pretty much
 undocumented. I need at least a format for easy reading by humans and a
 single-line compact format for use in a protocol, and preferably a way to
-generate ASCII-only JSON strings).
+generate ASCII-only JSON texts).
 Completely broken (and confusingly documented) Unicode handling (unicode
 escapes are not working properly, you need to set ImplicitUnicode to
 I<different> values on en- and decoding to get symmetric behaviour).
 Very inflexible.
 No roundtripping.
-Does not generate valid JSON (key strings are often unquoted, empty keys
+Does not generate valid JSON texts (key strings are often unquoted, empty keys
 result in nothing being output)
 Does not check input for validity.
 =back
 It seems that JSON::XS is surprisingly fast, as shown in the following
 tables. They have been generated with the help of the C<eg/bench> program
 in the JSON::XS distribution, to make it easy to compare on your own
 system.
-First is a comparison between various modules using a very simple JSON
+First comes a comparison between various modules using a very short JSON
+string:
+   {"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}
-string, showing the number of encodes/decodes per second (JSON::XS is
+It shows the number of encodes/decodes per second (JSON::XS uses the
-the functional interface, while JSON::XS/2 is the OO interface with
+functional interface, while JSON::XS/2 uses the OO interface with
-pretty-printing and hashkey sorting enabled).
+pretty-printing and hashkey sorting enabled). Higher is better:
    module     |     encode |     decode |
    -----------|------------|------------|
-   JSON       |      14006 |       6820 |
+   JSON       |  11488.516 |   7823.035 |
-   JSON::DWIW |     200937 |     120386 |
+   JSON::DWIW |  94708.054 | 129094.260 |
-   JSON::PC   |      85065 |     129366 |
+   JSON::PC   |  63884.157 | 128528.212 |
-   JSON::Syck |      59898 |      44232 |
+   JSON::Syck |  34898.677 |  42096.911 |
-   JSON::XS   |    1171478 |     342435 |
+   JSON::XS   | 654027.064 | 396423.669 |
-   JSON::XS/2 |     730760 |     328714 |
+   JSON::XS/2 | 371564.190 | 371725.613 |
    -----------+------------+------------+
-That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80
+That is, JSON::XS is more than six times faster than JSON::DWIW on
+encoding, more than three times faster on decoding, and about thirty times
-times faster than JSON, even with pretty-printing and key sorting.
+faster than JSON, even with pretty-printing and key sorting.
-Using a longer test string (roughly 8KB, generated from Yahoo! Locals
+Using a longer test string (roughly 18KB, generated from Yahoo! Locals
 search API (http://nanoref.com/yahooapis/mgPdGg):
    module     |     encode |     decode |
    -----------|------------|------------|
-   JSON       |        673 |         38 |
+   JSON       |    273.023 |     44.674 |
-   JSON::DWIW |       5271 |        770 |
+   JSON::DWIW |   1089.383 |   1145.704 |
-   JSON::PC   |       9901 |       2491 |
+   JSON::PC   |   3097.419 |   2393.921 |
-   JSON::Syck |       2360 |        786 |
+   JSON::Syck |    514.060 |    843.053 |
-   JSON::XS   |      37398 |       3202 |
+   JSON::XS   |   6479.668 |   3636.364 |
-   JSON::XS/2 |      13765 |       3153 |
+   JSON::XS/2 |   3774.221 |   3599.124 |
    -----------+------------+------------+
-Again, JSON::XS leads by far in the encoding case, while still beating
+Again, JSON::XS leads by far.
-every other module in the decoding case.
-Last example is an almost 8MB large hash with many large binary values
+On large strings containing lots of high unicode characters, some modules
-(PNG files), resulting in a lot of escaping:
+(such as JSON::PC) seem to decode faster than JSON::XS, but the result
+will be broken due to missing (or wrong) unicode handling. Others refuse
+to decode or encode properly, so it was impossible to prepare a fair
+comparison table for that case.
+=head1 SECURITY CONSIDERATIONS
+When you are using JSON in a protocol, talking to untrusted potentially
+hostile creatures requires relatively few measures.
+First of all, your JSON decoder should be secure, that is, should not have
+any buffer overflows. Obviously, this module should ensure that and I am
+trying hard on making that true, but you never know.
+Second, you need to avoid resource-starving attacks. That means you should
+limit the size of JSON texts you accept, or make sure then when your
+resources run out, thats just fine (e.g. by using a separate process that
+can crash safely). The size of a JSON text in octets or characters is
+usually a good indication of the size of the resources required to decode
+it into a Perl structure.
+Third, JSON::XS recurses using the C stack when decoding objects and
+arrays. The C stack is a limited resource: for instance, on my amd64
+machine with 8MB of stack size I can decode around 180k nested arrays
+but only 14k nested JSON objects. If that is exceeded, the program
+crashes. Thats why the default nesting limit is set to 8192. If your
+process has a smaller stack, you should adjust this setting accordingly
+with the C<max_depth> method.
+And last but least, something else could bomb you that I forgot to think
+of. In that case, you get to keep the pieces. I am alway sopen for hints,
+though...
 =head1 BUGS
 While the goal of this module is to be correct, that unfortunately does
 not mean its bug-free, only that I think its design is bug-free. It is
-still very young and not well-tested. If you keep reporting bugs they will
+still relatively early in its development. If you keep reporting bugs they
-be fixed swiftly, though.
+will be fixed swiftly, though.
 =cut
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Comparing JSON-XS/XS.pm (file contents): Revision 1.10 by root, Fri Mar 23 17:40:29 2007 UTC vs. Revision 1.23 by root, Sun Mar 25 21:19:13 2007 UTC

Diff Legend

Comparing JSON-XS/XS.pm (file contents):
Revision 1.10 by root, Fri Mar 23 17:40:29 2007 UTC vs.
Revision 1.23 by root, Sun Mar 25 21:19:13 2007 UTC